In a wireless power transfer system, the amount of power and the efficiency of the power transfer are affected by many factors. As a few of many examples, distance between power transfer coils, orientation of coils, and number and type of objects in the vicinity all affect power transfer. As coupling between the coils decreases, from the above illustrative factors or other factors, power transfer tends to decrease.
Power transfer is increased when both the transmitter and receiver in a wireless power transfer system are operating at the same resonance frequency. In some systems, the resonance frequency of one or both of the transmitter and receiver may be tuned by adjusting a circuit parameter.
It is desirable to have the capability to tune the transmitter based solely on information measured or retrieved from within the transmitter, or to tune the receiver based solely on information measured or retrieved from within the receiver.